FILE - In this Sunday, Aug. 17, 2014, file photo, police wait to advance after tear gas was used to disperse a crowd during a protest for Michael Brown, who was killed by a police officer on Aug. 9, in Ferguson, Mo. The national legal standards that govern when police officers are justified using force against people trace their lineage to a 1984 case from Charlotte, N.C. Brown's shooting has prompted multiple investigations and triggered days of rioting reflecting long-simmering racial tensions in a town of mostly black residents and a majority white police force. (AP Photo/Charlie Riedel, File)

WASHINGTON (AP) — The moment Ferguson, Missouri, police officer Darren Wilson shot an unarmed teenager, a 25-year-old Supreme Court case became the prism through which his actions will be legally judged.

To most people, an 18-year-old unarmed man may not appear to pose a deadly threat. But a police officer’s perspective is different. And that is how an officer should be judged after the fact, Chief Justice William Rehnquist wrote in the 1989 opinion.

The Supreme Court case, decided at a time when violence against police was on the rise, has shaped the national legal standards that govern when police officers are justified in using force. The key question about Wilson’s killing on Aug. 9 is whether a reasonable officer with a similar background would have responded the same way.

The sequence of events that led to the death of Michael Brown, a black man shot by a white officer, remains unclear. An autopsy paid for by Brown’s family concluded that he was shot six times, twice in the head. The shooting has prompted multiple investigations and touched off days of rioting reflecting long-simmering racial tensions in a town of mostly black residents and a majority white police force.

Attorney General Eric Holder said Thursday the episode had opened a national conversation about “the appropriate use of force and the need to ensure fair and equal treatment for everyone who comes into contact with the police.”

A grand jury is hearing evidence to determine whether Wilson, 28, who has policed the St. Louis suburbs for six years, should be charged in Brown’s death.

Since the 1989 Graham v. Connor decision, the courts in most instances have sided with the police.

“Except in the most outrageous cases of police misconduct, juries tend to side with police officers and give them a lot of leeway,” said Woody Connette, the attorney who represented the Charlotte, North Carolina, man behind the case, Dethorne Graham.

On Nov. 12, 1984, Graham, 39, felt the onset of an insulin reaction, and asked a friend to drive him to buy orange juice that would increase his blood sugar, Connette said.

According to the Supreme Court, Graham rushed into the store and grabbed the orange juice but saw the checkout line was too long, so he put the juice down and ran back to the car.

Charlotte police officer M.S. Connor thought this was suspicious and followed him. When Connor stopped Graham’s friend’s car, Graham explained he was having a sugar reaction. But Connor didn’t believe him.

As Connor was following up with the store to see whether anything had happened, Graham left the car, ran around it twice, then sat down and passed out for a short time. Other police officers arrived, and Graham was rolled over and handcuffed. The officers lifted Graham from behind and placed him face down on the car.

When Graham asked the officers to check his pocket for something he carried that identified him as a diabetic, one of the officers told him to “shut up” and shoved his face against the hood of the car. Then four officers grabbed Graham and threw him head-first into the police car. Once police confirmed no crime had been committed inside the convenience store, they dropped Graham off at his home and left him lying in the yard, Connette said.

Graham ended up with a broken foot, cuts on his wrists, a bruised forehead and an injured shoulder.

Graham, who died in 2000, lost his lawsuit against the city of Charlotte and five police officers in a jury trial and appealed all the way to the Supreme Court, which set out the standards still used today. After the Supreme Court decision vacating an appeals court ruling against Graham, he had a new trial, in which the police actions were judged on new standards. Graham lost again.

The Graham decision found that an officer’s use of force should be considered on the facts of each case. Officers are to weigh the seriousness of the crime, whether the suspect poses a threat to the safety of police or others and whether the suspect is trying to resist arrest.

“The ‘reasonableness’ of a particular use of force must be judged from the perspective of a reasonable officer on the scene, rather than with the 20/20 vision of hindsight,” Rehnquist wrote.

In Graham’s case, his behavior as he was experiencing low blood sugar looked similar to that of a belligerent drunk.

Since then, police officers across the U.S. have been trained to use force in that context. States and police departments have their own policies, but the standards set in the Graham case are always the minimum. Some law enforcement agencies, like the Los Angeles Police Department, even reference Graham v. Connor in their manuals.

The jury that acquitted four Los Angeles police officers in the beating of Rodney King in 1991 was instructed to consider the Graham standards — the officers’ “reasonable perceptions” — as they deliberated.

Officers are to be judged by those standards even if things look different to people who weren’t involved.

“What a police officer, what she perceives at the moment of application of force, may seem very different in the hard light of the following Monday morning,” said Ken Wallentine, a recently retired police chief and former law professor in Utah. “And there’s the rub.”

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